Oral Glutamine Challenge Research Articles

Oral glutamine challenge is a marker of altered ammonia metabolism and predicts the risk of hepatic encephalopathy.

The current therapies for hepatic encephalopathy (HE) are not completely effective in all patients, probably due to the physiopathological heterogeneity and the different conditions underlying the bout of HE. We hypothesized that oral glutamine challenge (OGC) is able to predict the risk of HE through the identification of various features and types of HE. We included 238 cirrhotic patients (198 without and 40 with a previous HE episode) that underwent OGC, obtaining baseline and 60minutes post-load ammonia levels. Combined evaluation of baseline hyperammonemia (>78mcg/dL) and impaired OGC (Δ >32mcg/dL) defined low-, intermediate- and high-risk groups. Patients were censored at HE, liver transplantation and death or 6years of follow-up. The 28.3% (56/198) of the main cohort suffered from HE during the follow-up. In the competing risk analysis, both intermediate- (subhazard ratio (sHR) 2.01 (95% CI 1.00-4.14); P=.048) and high-risk groups (sHR 4.67 (95% CI 2.19-9.98); P=.0001) were associated with the first HE episode, together with age and albumin. Similar results were found for repeated HE events. The cumulative incidence for HE of the high-risk group was two and four times greater than the intermediate- and low-risk groups, respectively. The HE grade was also higher in individuals with the greatest risk (P=.035). The most common precipitant factor was diuretics in the high-risk group, while infections and electrolyte imbalance predominated in the rest of patients. Oral glutamine challenge identified patients at risk of HE and defined specific features of the episodes. This tool could be useful in the decision-making process for the adequate management of HE.

FRI-026 - Oral glutamine challenge predicts risk and defines hepatic encephalopathy types

FRI-026 - Oral glutamine challenge predicts risk and defines hepatic encephalopathy types

203 ORAL GLUTAMINE CHALLENGE – DOES IT IMPROVE REVEALING MINIMAL HEPATIC ENCEPHALOPATHY IN CIRRHOSIS?

Background and Aims: Minimal hepatic encephalopathy (MHE) is a prevalent asymptomatic condition, whose diagnosis is difficult due to the lack of a gold standard test. Oral glutamine challenge (OGC) has been found to increase blood ammonia in patients with cirrhosis which could lead to significant cognitive impairment. The aim of our study was to evaluate the value of OGC in improving the performance of psychometric tests and arterial blood ammonia for the diagnosis of MHE. Secondary we followed the risk for development of overt hepatic encephalopathy (OHE). Methods: Fifty-four patients (male/female: 34/20; mean age 59.5yrs) with cirrhosis and 13 healthy controls matched by sex and age were included. Follow-up lasted 12 months. MHE was assessed using the psychometric hepatic encephalopathy score (PHES). Arterial ammonia blood concentrations and PHES were evaluated preand post-60 minutes of a 20 g oral glutamine load. Statistical analysis used paired t-test, relative operating characteristics (ROC) and multivariate logistic regression analysis. Results: At baseline, 29 (53.7%) out of 54 patients met the criteria for MHE, while post glutamine challenge, 43 patients (79.63%) had MHE (p < 0.0001). Arterial blood ammonia levels had significantly raised after glutamine challenge in the cirrhotic patients (baseline vs post glutamine: 85.2±20.8mg/dL vs 159.82±66.01mg/dL, p < 0.0001) as compared to controls values which remained unchanged. ROC analysis showed a pathological glutamine tolerance cut-off value of 124mg/dl. For baseline arterial blood ammonia the AUROC was 0.54 (CI: 0.402–0.680, p = 0.58), with no significant change post glutamine challenge (AUROC = 0.53, CI: 0.389–0.667, p = 0.77). In the follow-up 16 patients (29.62%) developed OHE. In multivariate model, MELD score (OR = 1.5187, 95%CI: 1.0690–2.1574, P = 0.0197), but not Child Pugh class, arterial blood ammonia, esophageal varices grading, was a strong independent predictor of OHE. Conclusions: In cirrhotic patients, OGC appears to improve the performance of psychometric tests, but not arterial blood ammonia for the diagnosis of MHE. MELD score has proven to be independently related with OHE in the follow up. Acknowledgements: This work was made possible by the project ‘Doctoral Scholarships for increasing competitiveness in the medical and pharmaceutical field’ POSDRU/88/1.5/S/58965.

Metformin inhibits glutaminase activity and protects against hepatic encephalopathy.

AimTo investigate the influence of metformin use on liver dysfunction and hepatic encephalopathy in a retrospective cohort of diabetic cirrhotic patients. To analyze the impact of metformin on glutaminase activity and ammonia production in vitro.MethodsEighty-two cirrhotic patients with type 2 diabetes were included. Forty-one patients were classified as insulin sensitizers experienced (metformin) and 41 as controls (cirrhotic patients with type 2 diabetes mellitus without metformin treatment). Baseline analysis included: insulin, glucose, glucagon, leptin, adiponectin, TNFr2, AST, ALT. HOMA-IR was calculated. Baseline HE risk was calculated according to minimal hepatic encephalopathy, oral glutamine challenge and mutations in glutaminase gene. We performed an experimental study in vitro including an enzymatic activity assay where glutaminase inhibition was measured according to different metformin concentrations. In Caco2 cells, glutaminase activity inhibition was evaluated by ammonia production at 24, 48 and 72 hours after metformina treatment.ResultsHepatic encephalopathy was diagnosed during follow-up in 23.2% (19/82): 4.9% (2/41) in patients receiving metformin and 41.5% (17/41) in patients without metformin treatment (logRank 9.81; p = 0.002). In multivariate analysis, metformin use [H.R.11.4 (95% CI: 1.2–108.8); p = 0.034], age at diagnosis [H.R.1.12 (95% CI: 1.04–1.2); p = 0.002], female sex [H.R.10.4 (95% CI: 1.5–71.6); p = 0.017] and HE risk [H.R.21.3 (95% CI: 2.8–163.4); p = 0.003] were found independently associated with hepatic encephalopathy. In the enzymatic assay, glutaminase activity inhibition reached 68% with metformin 100 mM. In Caco2 cells, metformin (20 mM) decreased glutaminase activity up to 24% at 72 hours post-treatment (p<0.05).ConclusionsMetformin was found independently related to overt hepatic encephalopathy in patients with type 2 diabetes mellitus and high risk of hepatic encephalopathy. Metformin inhibits glutaminase activity in vitro. Therefore, metformin use seems to be protective against hepatic encephalopathy in diabetic cirrhotic patients.

A capillary blood ammonia bedside test following glutamine load to improve the diagnosis of hepatic encephalopathy in cirrhosis

BackgroundHepatic encephalopathy (HE) is a frequent and severe complication of cirrhosis. A single determination of ammonia in venous blood correlates poorly with neurological symptoms. Thus, a better biological marker is needed.AimTo make a diagnosis of HE, we explored the value of ammonia in capillary blood, an equivalent to arterial blood, measured at bedside following an oral glutamine challenge.MethodsWe included 57 patients (age 56 yrs; M/F: 37/20) with cirrhosis (alcoholic = 42; MELD score 13.8 [7-29], esophageal varices = 38) and previous episodes of HE (n = 19), but without neurological deficits at time of examination, and 13 healthy controls (age 54 yrs). After psychometric tests and capillary (ear lobe) blood ammonia measurements, 20 gr of glutamine was administered orally. Tests were repeated at 60 minutes (+ blood ammonia at 30'). Minimal HE was diagnosed if values were > 1.5 SD in at least 2 psychometric tests. Follow-up lasted 12 months.ResultsThe test was well tolerated (nausea = 1; dizziness = 1). Patients showed higher values of capillary blood ammonia over time as compared to controls (0'-30'-60 minutes: 75, 117, 169 versus 52, 59, 78 umol/L, p < 0.05). At baseline, 25 patients (44%) had minimal HE, while 38 patients (67%) met the criteria for HE at 60 minutes (chi2: p < 0.01). For the diagnosis of minimal HE, using the ROC curve analysis, baseline capillary blood ammonia showed an AUC of 0.541 (CI: 0.38-0.7, p = 0.6), while at 60 minutes the AUC was 0.727 (CI: 0.58-0.87, p < 0.006). During follow-up, 18 patients (31%) developed clinical episodes of HE. At multivariate analysis, the MELD score (1.12 [1.018-1.236]), previous episodes of HE (3.2[1.069-9.58]), but not capillary blood ammonia, were independent predictors of event.ConclusionsIn patients with cirrhosis and normal neurological examination, bedside determination of ammonia in capillary blood following oral glutamine load is well tolerated and achieves a better diagnostic performance for minimal HE than basal capillary ammonia levels. However, capillary blood ammonia is a poor predictor of development of clinically overt HE.

Rat CCl4-induced cirrhosis plus total portal vein ligation: a new model for the study of hyperammonaemia and brain oedema

Animal models used to study hyperammonaemic disorders related to chronic liver disease are unsatisfactory. These animals only develop hyperammonaemia and brain oedema when fed with diets supplemented with amonium acetate. To develop a novel experimental model of hyperammonaemia and brain oedema in CCl(4)-induced cirrhosis in rats. Four groups were studied: rats with sham intervention (S), rats with total portal vein ligation (TPVL), cirrhotic rats (LC), and cirrhotic rats with TPVL (LC+TPVL). When ascites was diagnosed, oral glutamine challenge (OGC) test was performed. Blood, liver, lungs and brain samples were collected to quantify liver function parameters, plasmatic and cerebral ammonia, endotoxaemia, liver and brain histology, brain oedema and portosystemic shunting degree. LC+TPVL rats showed a significant increase in portosystemic shunting when compared with LC group and a significant derangement in liver function when compared with TPVL group. These alterations resulted in a significant increase in plasmatic and brain ammonia concentrations and a higher plasmatic endotoxaemia as compared with others. Similarly, the area under OGC curve was significantly increased in LC+TPVL group as compared with the others, and correlates with portal shunting. Low-grade brain oedema was only observed in LC+TPVL group. All cirrhotic groups showed liver regeneration nodules and type-II Alzheimer astrocytes LC+TPVL reproduce the main alterations - portosystemic shunting, plasmatic and cerebral hyperammonaemia and low-grade brain oedema - observed in cirrhotic patients with hepatic encephalopathy.

S1925 Clinical Efficacy of L-Ornithine L-Aspartate in the Prevenction of Altered Oral Glutamine Challenge in Patients With Minimal Hepatic Encephalopathy: A Pilot Study

S1925 Clinical Efficacy of L-Ornithine L-Aspartate in the Prevenction of Altered Oral Glutamine Challenge in Patients With Minimal Hepatic Encephalopathy: A Pilot Study

Gut ammonia production and its modulation

Systemic hyperammonemia has been largely found in patients with cirrhosis and hepatic encephalopathy, and ammonia plays a major role in the pathogenesis of hepatic encephalopathy. However, controversial points remain: a) the correlation between plasma ammonia levels and neurophysiological impairment. The lack of correlation between ammonia levels and grade of hepatic encephalopathy in some cases has been considered a weakness of the ammonia hypothesis, but new methods for ammonia measurements and the implication of systemic inflammation in the modulation of ammonia neurotoxicity could explain this gap; b) the source of ammonia production. Hyperammonemia has been considered as derived from urea breakdown by intestinal bacteria and the majority of treatments were targeted against bacteria-derived ammonia from the colon. However, some data suggest an important role for small intestine ammonia production: 1) the hyperammonemia after porto-caval shunted rats has been found similar in germ-free than in non-germ-free animals. 2) In cirrhotic patients the greatest hyperammonemia was found in portal drained viscera and derived mainly from glutamine deamination. 3) The amount of time required to increase of ammonia (less than one hour) after oral glutamine challenge supports a small intestine origin of the hyperammonemia. As the main source of ammonia in cirrhotics derives from portal drained viscera owing to glutamine deamidation, increased glutaminase activity in the intestine seems to be responsible for systemic hyperammonemia. Lastly, some genetic alterations in the glutaminase gene such as the haplotype TACC could modulate intestinal ammonia production and the risk of overt hepatic encephalopathy in cirrhotics.

Noncirrhotic portal vein thrombosis exhibits neuropsychological and MR changes consistent with minimal hepatic encephalopathy†

Hepatic encephalopathy can arise from portal-systemic shunting in the absence of intrinsic liver disease. However, there are few descriptions of this form of encephalopathy. Portal vein thrombosis is an infrequent disease that causes portal-systemic shunting. Episodic hepatic encephalopathy has been described in patients with portal vein thrombosis, but it is not known if these patients develop minimal hepatic encephalopathy. We designed a study to investigate the neurological consequences of portal vein thrombosis in patients without cirrhosis and no clinical signs of encephalopathy. For this purpose, 10 patients underwent neuropsychological tests, an oral glutamine challenge test, and brain magnetic resonance (MR) imaging. The results were compared with those obtained in 10 healthy controls. Patients with portal vein thrombosis exhibited abnormalities in the results of neuropsychological tests, oral glutamine challenge test, and MR similar to those described in hepatic encephalopathy associated with cirrhosis. MR spectroscopy revealed a decrease in myo-inositol and an increase in glutamine. The increase in glutamine correlated with an increase in ammonia following the oral glutamine challenge test, signs of increased brain water (decrease in magnetization transfer ratio), and impairment of attention tests. In conclusion, patients with noncirrhotic portal vein thrombosis develop subclinical neurological abnormalities compatible with minimal hepatic encephalopathy. These disturbances, which include signs of increase in brain water and a compensatory osmotic response (decrease in brain myo-inositol), appear to be secondary to brain exposure to ammonia induced by portal-systemic shunting.

182 Oral glutamine challenge response is regulated by portal hypertension and systemic inflammatory response

182 Oral glutamine challenge response is regulated by portal hypertension and systemic inflammatory response

Intestinal glutaminase activity is increased in liver cirrhosis and correlates with minimal hepatic encephalopathy

Background/Aims We performed the current study to assess the intestinal activity of enterocyte phosphate-activated glutaminase (PAG) in cirrhosis. Methods Forty-nine cirrhotic patients and 36 control subjects underwent endoscopic duodenal biopsies. Minimal hepatic encephalopathy (MHE) was evaluated using three psychometric tests. Oral glutamine challenge (OGC) was performed and MELD, Child-Pugh and the presence of esophageal varices were recorded. PAG was measured by enzymatic methods. Cerebral magnetic resonance spectroscopy was performed in 10 cirrhotics. Results PAG was found to be higher in cirrhotics than control subjects 2.4±1.51 vs. 0.68±0.57 IU/mg protein ( P<0.001). PAG was also increased in patients with MHE and correlated with MELD, INR, esophageal varices and serum bile acids. A negative correlation was observed between PAG activity and intra-cerebral choline/creatine ratio ( r=−0.67; P=0.035) and a positive correlation with glutamine plus glutamate/creatine ratio ( r=0.78; P=0.007). In multivariate analysis using backward logistic regression, presence of MHE was the only variable independently related to altered enterocyte PAG. Conclusions Enterocyte PAG is increased in cirrhotic patients and correlates with MHE. These data support a possible role for intestinal glutaminase in the pathogenesis of hepatic encephalopathy (HE) and could be a new target for future therapies.

Oral glutamine challenge and magnetic resonance spectroscopy in three patients with congenital portosystemic shunts

Background/Aims Congenital portosystemic shunts are rare abnormalities of liver vasculature that can cause neurological symptoms, probably secondarily to the effects of the metabolism of ammonia in the brain. Our aim was to investigate the relationship between capillary blood ammonia after oral glutamine challenge and magnetic resonance spectroscopy in three patients with congenital portosystemic shunts. Methods Neuropsychological tests, oral glutamine challenge and magnetic resonance spectroscopy were performed at baseline and after 6 months of follow-up in three patients with congenital portosystemic shunts. The results were compared to those obtained in a group of six cirrhotic patients with prior episodes of hepatic encephalopathy and healthy controls. Results Patients with congenital portosystemic shunts exhibited abnormalities of neuropsychological tests, magnetic resonance spectroscopy and a response to the oral glutamine challenge similar to those observed in patients with cirrhosis. The intensity of the rise of brain glutamine was correlated to the area under the curve of ammonia after the oral glutamine challenge ( R=0.72). Conclusions Neurological manifestations of patients with congenital portosystemic shunts are mediated through similar mechanisms that are involved in the pathogenesis of hepatic encephalopathy. The area under the curve appears to be the better parameter that defines the response to the oral glutamine challenge.

Altered response to oral glutamine challenge as prognostic factor for overt episodes in patients with minimal hepatic encephalopathy

Background/Aims: We assessed the usefulness of oral glutamine challenge (OGC) and minimal hepatic encephalopathy in evaluating risk of overt hepatic encephalopathy in cirrhotic patients. Methods: Minimal hepatic encephalopathy (MHE) was inferred using neuro-psychological tests. Venous ammonia concentrations were measured pre- and post-60 min (NH 3-60m) of a 10 g oral glutamine load. Receiver-operating-characteristic curve analysis indicated a pathological glutamine tolerance cut-off value of NH 3-60m >128 μg/dl. Results: In healthy control subjects ( n=10) ammonia concentrations remained unchanged but increased significantly in cirrhotic patients (from 70.41±45.2 to 127.43±78.6; P<0.001). In multiple logistic regression analysis, altered OGC was related to Child-Pugh (odds ratio, OR=7.69; 95% confidence interval, CI=1.72–33.3; P<0.01) and MHE (OR=5.45; 95% CI=1.17–25.4; P<0.05). In the follow-up 11 patients (15%) developed overt hepatic encephalopathy (HE). In multivariate analysis OGC (OR=14.5; 95% CI=1.26–126.3) and MHE (OR=1.56; 95% CI=1.02–21.9) were independently related with HE in the follow-up. Patients with MHE and altered OGC showed significantly higher risk of overt HE in the follow-up (60%) than patients without MHE and normal OGC (2.8%) (Log rank test=21.60; P<0.0001). Conclusions: A pathological OGC in patients with MHE appears to be a prognostic factor for the development of overt hepatic encephalopathy, whereas a normal OGC in patients without MHE could exclude risk of overt HE.

Oral glutamine challenge correlates with minimal hepatic encephalopathy and predicts overt episodes

Oral glutamine challenge correlates with minimal hepatic encephalopathy and predicts overt episodes

Oral glutamine challenge in patients with subclinical hepatic encephalopathy

Oral glutamine challenge in patients with subclinical hepatic encephalopathy

Oral glutamine challenge in patients with subclinical hepatic encephalopathy

Oral glutamine challenge in patients with subclinical hepatic encephalopathy

Effect of sodium benzoate on blood ammonia response to oral glutamine challenge in cirrhotic patients: a note of caution

OBJECTIVE: The administration of sodium benzoate provides an alternative pathway for the disposal of waste nitrogen and this substance has been used to treat patients with urea cycle defects and more recently cirrhotics with hepatic encephalopathy. The aim of the study was to assess the ammonia-lowering effect of benzoate in cirrhotic patients without overt hepatic encephalopathy. METHODS: Glutamine challenge, a method to induce an increase of blood ammonia, was performed in six cirrhotics before and after 5 days of benzoate treatment (10 g/day). Number Connection Test and Posner’s Attention Test were also performed before and after benzoate treatment. RESULTS: Blood ammonia increased after the glutamine load both before (from 66 ± 12 μg/dl to 123 ± 34 μg/dl and 179 ± 53 μg/dl after 30 and 60 min, respectively; ANOVA p = 0.0004) and after benzoate treatment (from 102 ± 27 μg/dl to 185 ± 49 μg/dl and 250 ± 39 μg/dl after 30 and 60 min, respectively; ANOVA p = 0.00001). However, after benzoate treatment, the basal values (102 ± 27 vs 66 ± 12 μg/dl; p = 0.01) and peak increments of ammonia (166 ± 56 μg/dl vs 102 ± 40 μg/dl; p = 0.04) were significantly higher than before. The Number Connection test and the Posner’s test were not altered by benzoate treatment. CONCLUSIONS: Benzoate increased both the basal and postglutamine ammonia levels. These results confirm what has already been observed in experimental animals and suggest a note of caution in the use of sodium benzoate in cirrhotic patients.

Effect of sodium benzoate on blood ammonia response to oral glutamine challenge in cirrhotic patients: a note of caution.

The administration of sodium benzoate provides an alternative pathway for the disposal of waste nitrogen and this substance has been used to treat patients with urea cycle defects and more recently cirrhotics with hepatic encephalopathy. The aim of the study was to assess the ammonia-lowering effect of benzoate in cirrhotic patients without overt hepatic encephalopathy. Glutamine challenge, a method to induce an increase of blood ammonia, was performed in six cirrhotics before and after 5 days of benzoate treatment (10 microg/day). Number Connection Test and Posner's Attention Test were also performed before and after benzoate treatment. Blood ammonia increased after the glutamine load both before (from 66 +/- 12 microg/dl to 123 +/- 34 microg/dl and 179 +/- 53 microg/dl after 30 and 60 min, respectively; ANOVA p = 0.0004) and after benzoate treatment (from 102 +/- 27 microg/dl to 185 +/- 49 microg/dl and 250 +/- 39 microg/dl after 30 and 60 min, respectively; ANOVA p = 0.00001). However, after benzoate treatment, the basal values (102 +/- 27 vs 66 +/- 12 microg/dl; p = 0.01) and peak increments of ammonia (166 +/- 56 microg/dl vs 102 +/- 40 microg/dl; p = 0.04) were significantly higher than before. The Number Connection test and the Posner's test were not altered by benzoate treatment. Benzoate increased both the basal and post-glutamine ammonia levels. These results confirm what has already been observed in experimental animals and suggest a note of caution in the use of sodium benzoate in cirrhotic patients.

Effect of lactitol on blood ammonia response to oral glutamine challenge in cirrhotic patients: evidence for an effect of nonabsorbable disaccharides on small intestine ammonia generation

OBJECTIVE: Nonabsorbable disaccharides are widely used to decrease blood ammonia concentration. Their principal mode of action is the modification of pH and bacterial flora in the colon. The aim of the present study was to test the hypothesis that these drugs may also reduce small intestine ammonia generation. METHODS: Eight male cirrhotics without overt hepatic encephalopathy received 20 g of glutamine in 100 ml of water. Venous samples for whole blood ammonia were taken before, 30 and 60 min after the load. Immediately after the last blood sample the patients were submitted to the following psychometric tests: number connection test, Posner’s attention test, and Sternberg paradigm. After the first glutamine load, patients were started on lactitol (initial dose 20 g, three times a day). Once two bowel movements/day were obtained and maintained for at least 5 days, oral glutamine challenge and psychometric tests were repeated. RESULTS: Ammonia increased significantly after the glutamine load (from 83 ± 13 to 164 ± 30 μg/dl at 30 min and 210 ± 29 μg/dl at 60 min; mean ±SE; p = 0.006 analysis of variance) but not after glutamine load after lactitol treatment (from 77 ± 17 to 111 ± 21 μg/dl and 142 ± 24 μg/dl; p = not significant). The peak increment (127 ± 24 vs 65 ± 18 μg/dl; p = 0.008) of ammonia elevation was significantly smaller during lactitol administration. The patients’ psychometric performance after the glutamine load did not differ significantly after lactitol treatment. CONCLUSIONS: Lactitol reduces the elevation in blood ammonia that follows oral glutamine challenge. Because enterally administered glutamine is efficiently absorbed in the jejunum and, in part, metabolized to ammonia we suggest that lactitol affects small intestine ammonia generation probably by shortening the residence time of intestinal contents.

Effect of lactitol on blood ammonia response to oral glutamine challenge in cirrhotic patients: evidence for an effect of nonabsorbable disaccharides on small intestine ammonia generation.

Nonabsorbable disaccharides are widely used to decrease blood ammonia concentration. Their principal mode of action is the modification of pH and bacterial flora in the colon. The aim of the present study was to test the hypothesis that these drugs may also reduce small intestine ammonia generation. Eight male cirrhotics without overt hepatic encephalopathy received 20 g of glutamine in 100 ml of water. Venous samples for whole blood ammonia were taken before, 30 and 60 min after the load. Immediately after the last blood sample the patients were submitted to the following psychometric tests: number connection test, Posner's attention test, and Sternberg paradigm. After the first glutamine load, patients were started on lactitol (initial dose 20 g, three times a day). Once two bowel movements/day were obtained and maintained for at least 5 days, oral glutamine challenge and psychometric tests were repeated. Ammonia increased significantly after the glutamine load (from 83 +/- 13 to 164 +/- 30 microg/dl at 30 min and 210 +/- 29 microg/dl at 60 min; mean +/- SE; p = 0.006 analysis of variance) but not after glutamine load after lactitol treatment (from 77 +/- 17 to 111 +/- 21 microg/dl and 142 +/- 24 microg/dl; p = not significant). The peak increment (127 +/- 24 vs 65 +/- 18 microg/dl; p = 0.008) of ammonia elevation was significantly smaller during lactitol administration. The patients' psychometric performance after the glutamine load did not differ significantly after lactitol treatment. Lactitol reduces the elevation in blood ammonia that follows oral glutamine challenge. Because enterally administered glutamine is efficiently absorbed in the jejunum and, in part, metabolized to ammonia we suggest that lactitol affects small intestine ammonia generation probably by shortening the residence time of intestinal contents.